Urban Heat Islands & Climate Change

Urban heat islands are regions that experience higher temperatures than surrounding areas, primarily due to the concentration of buildings, roads and other structures that absorb and re-emit heat. As climate change leads to higher temperatures, urban heat values are likely to increase. In Missouri, high summer temperatures and high humidity are exacerbated in urban areas, where temperatures can be 2 to 10 degrees hotter than their surroundings. This can increase overall energy use and lead to dangerous conditions for those without access to air conditioning or other ways to stay cool (e.g., green roofs, weatherproof buildings). Scientific research indicates that green infrastructure, including cool pavement, tree canopies and park space within urban areas, is an effective way to offset urban heat island effects. 

Science Highlights

• Urban heat islands are caused by reduced vegetation cover in urban areas.
• Increased urban heat is a consequence of development and climate change. 
• The health and economic consequences of extreme heat disproportionately impact low-income households, people with chronic health problems, older adults and kids.
• EPA recommends green infrastructure to moderate urban heat islands, such as increasing the urban tree canopy and building green roofs.

Limitations

• In hot and humid areas like Missouri, vegetation that dissipates heat through evaporation can increase humidity and counteract the benefits of increased evaporative cooling on the hottest nights. There is not enough information to determine the optimal level of vegetation to reduce heat in humid areas.